Method and apparatus for treating filler-containing material, such as recycled fibers

ABSTRACT

Recycled fiber pulp from a vortex cleaning plant (e.g. connected to the short circulation of a paper machine) effects the recovery and return of fillers in the recycled fiber pulp discharged from the vortex cleaning plant, in an efficient and economical manner. The loss of filler in the recycled fiber pulp discharged from the vortex cleaning plant is decreased by treating a concentrated fraction of the rejects from the vortex cleaning plant with a mixer/disperser for dispersing the filler in the recycled fiber pulp, and returning as much usable filler as possible back to the process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the U.S. National Phase of International ApplicationNo. PCT/FI94/00086 filed Mar. 10, 1994.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a method and apparatus for treatingrecycled fibers and/or fraction exiting from the vortex cleaning as millreject. As is known, sources of recycled fibers include both the socalled broke of a paper machine, which may be rerecycled as rawmaterial, and the actual post-consumer waste paper and board. Thepresent invention especially relates to the treatment of such recycledfiber materials so that the fillers therein may be recovered as well aspossible and returned back to the process as efficiently andeconomically as possible.

In the short circulation of paper machines manufacturingfiller-containing paper grades and especially coated paper grades a lotof mineral and pigment fraction is discharged nowadays from the processas mill reject of a vortex cleaning plant, which of its content might beutilized as raw material for paper, but is of its particle size toocoarse.

In the short circulation of paper machines manufacturing SC grades andgrades containing other fillers, the mineral fraction exiting the vortexcleaning as mill reject is the coarse portion of the mineral fractionadded in the pulp dosing, the particle size being generally more than 10μm.

In the short circulation of paper machines manufacturing coated papergrades the mineral fraction exiting the process as mill reject mainlycontains non-dispersable coating layer of coated waste paper. Thecoating pigment has not dispersed in the dispersion system to particlesfine enough. The fraction of the coating pigment, which has not beendispersed and is of its size generally more than 10 μm, is rejected inthe vortex cleaning of the short circulation.

The same applies to systems for recycled pulp, in which coated newspaperor like heavily coated raw material for recycled paper is used as rawmaterial. In the defiberizing system for recycled pulp the coatingpigment of the coated paper is released from the actual fiber layer ofthe paper more or less in sheet-like fractions, which are partiallydispersed due to the process. The dispersion is, however, not completeand that is why these coating pigment particles which have remainednon-dispersed are discharged from the screening stage of the process asreject of the vortex cleaning. However, the majority of the particleswould be of their raw material content filler material usable in thepaper manufacture, which may possibly be added to the fiber suspensionin the later stages of the paper manufacture. The size of theseparticles is such that said particles cause problems in the papermanufacture if they are not dispersed and thus made qualified to be usedas fillers.

U.S. Pat. No. 4,504,016 discloses a process and apparatus for cleaningchemical cellulose by screening. The problem underlying the patent is toincrease the yield of chemical pulp in the production thereof. In theprocess the cellulose is sorted and a coarse fraction, i.e. knots andshives, is treated in a refiber and further sorted. Since it is aquestion of a chemical pulp manufacture process there are no furthersubstances e.g. filler material involved in the process. Also, thedocument teaches the removal of the rejects of the hydrocyclone out ofthe system.

U.S. Pat. No. 4,167,438 discloses a process and apparatus for preparingand cleaning fibrous material, e.g. mixed waste paper. The publicationteaches the combined recycle of both fibers and fillers back to use.There is no suggestion that the process could be used for separating andtreating the mere filler fraction of the waste paper pulp.

In an arrangement in accordance with the present invention the loss infillers/minerals exiting the vortex cleaning as mill reject isdiminished by treating fraction having a concentrated mineral content inthe vortex cleaning plant for dispersing mineral fractions and returningthem back to the process.

Advantages obtained by utilizing the method and apparatus in accordancewith the present invention are, for example, following:

Filler/mineral, water, chemical, heat and fiber losses are as low aspossible. Only useless fraction and fraction that cannot be changed intoa form that can be re-used are discharged in a very concentrated form.

Dispersion of mineral particles is based on internal shear forces of thesuspension, in other words mechanical wear is minimal.

Investment costs of the system are very low. Technical realization iscarried out with commercial apparatuses, repayment period is short.

System is easy to build, i.e. it may be mounted to the already existingsystems by adding a screening apparatus fractionating the mineralfraction and wood fraction separate and a new kind of cleaner for thedischarge of reject in a very concentrated form after the last cleanerstep and by adding a treatment stage dispersing the mineral fractionsthereafter.

Treatment is carried out, for example, in the short circulation of apaper machine for each machine individually, whereby, for example, thewater circulations between the machines are not mixed.

System is a continuously operating part of a short circulation of apaper machine, or of a screening system. In other words, the processconditions are constant and the operation trouble-free. Process adjustsitself, for example, if the amount of the coarse fraction increases, thesystem returns only the dispersed fraction to the process and the restis discharged from the system.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics of the method and apparatus in accordance with thepresent invention become apparent in the enclosed patent claims.

The method and apparatus in accordance with the present invention aredescribed more in detail below, by way of example, with reference to theaccompanying drawings, in which

FIGS. 1a and 1b schematically illustrate two filler treatment systems inaccordance with prior art;

FIG. 2 schematically illustrates a filler treatment system in accordancewith a preferred embodiment of the present invention;

FIG. 3 schematically illustrates a filler treatment system in accordancewith a second embodiment of the present invention;

FIG. 4 schematically illustrates a filler treatment system in accordancewith a third embodiment of the present invention;

FIG. 5 schematically illustrates a filler treatment system in accordancewith a fourth embodiment of the present invention;

FIG. 6 schematically illustrates a filler treatment system in accordancewith a fifth embodiment of the present invention;

FIG. 7 schematically illustrates a filler treatment system in accordancewith a sixth embodiment of the present invention;

FIG. 8 schematically illustrates a filler treatment system in accordancewith a seventh embodiment of the present invention;

FIG. 9 schematically illustrates one version of the system illustratedin FIG. 8; and

FIGS. 10a-c illustrate 100 times enlarged photographs of the materialfed to the curved screen of the apparatus in accordance with FIG. 8 andboth fractions obtained from the curved screen.

DETAILED DESCRIPTION OF THE DRAWINGS

An example of the prior art arrangements for diminishing filler/minerallosses is, for example, an arrangement in accordance with FIG. 1a. Therethe mineral loss is diminished by fractionating all fine material, i.e.solid material of useful size, from the flow exiting the process back tothe process. Said apparatus operates in such a way that the flow exitingfrom the process is brought to a curved screen 10, a so calledHydra-screen, which divides the flow into two fractions. The coarserfraction is led to an intermediate tank 12 and the finer fraction to afiltrate tank 14. The finer fraction is pumped from the filtrate tank 14by a pump 16 to a curved screen 18, a so called Micra-screen, of thesecondary stage, the coarser fraction of which is led to theintermediary tank 12 and the finer fraction, practically speaking clearliquid and the fine filler therewith to be reused, for example, for thedilutions necessary in the process. The fraction discharged from theintermediary tank 12 as reject of curved screens 10 and 18 is pumped bya pump 20, for example, to a filter press 22 for thickening the coarsefraction to a more useful consistency. In addition to a curved screen10, as in FIG. 1a, also a finely perforated/slotted pressure screen orvortex cleaners (FIG. 1b), such as so called trap cleaners commonly usedin sand separation may be used as a fractionation apparatus.

According to FIG. 1b the material to be treated is obtained as a rejectfrom the third or fourth step of a vortex cleaning plant 32, where thefine fraction rejected by the vortex cleaning plant 32 is led back touse. The material rejected from the vortex cleaning plant is led by apump 34 to a curved screen 36, preferably a so called Micra-screen, andthe liquid accepted by said curved screen 36, the so called filtrate, isled to the wire pit or, for example, to the dilution in a secondaryscreening apparatus. The reject of the curved screen 36, in other wordsthe thicker fraction, again, is led to the suction side of a pump 38,from where it is further pumped to a cleaner 39, preferably a so calledEliminator-cleaner, which is disclosed, for example, in U.S. Pat. No.5,139,652. The accept from the cleaner 39 is led to the suction side ofa feed pump 30 of the third or fourth step 32 of the vortex cleaningplant to be pumped again to the recirculation.

It is, however, characteristic of all said methods that they do notchange/diminish the particle size/distri-bution of the solids to betreated, but only separate the fine and as such usable fraction and thecoarse fraction and return the fine fraction to use.

It is a characteristic feature of a dispersion process of mineralfractions that it is based on internal shear forces of theflow/suspension which are mechanically generated. In order for the shearforces to have a dispersing effect in the suspension, in other words theshear forces to be effective enough, the concentration of the suspensionmust be high. Principally, the higher the concentration is, in which thetreatment takes place, the more efficient it is, in other words thegreater the shear forces are, which may be directed to the suspensionand the more efficiently the dispersion takes place.

The concentration of the mineral fraction is sufficiently increased bymeans of a new kind of vortex cleaner construction disclosed in U.S.Pat. No. 5,139,652, said cleaner being extremely efficient inclassifying, but from which the coarse mineral fraction, having the sizeof more than 10 μm, is rejected as a very concentrated flow having asolids content of even more than 40%.

The concentration of the fractions to be treated may be increased also,for example, by filtering or precipitating, but it is characteristic ofall these other methods that they require additional apparatuses and/orgreat volumes and are rather complicated to be carried out as acontinuous, trouble-free process. The concentration of the mineralfraction in a new kind of vortex cleaner takes place in connection withthe normal operation of the vortex cleaner without any additionalapparatuses.

After the thickening, i.e. the increase of the solids concentration, themineral fraction is treated by mechanical mixing elements or grindingapparatuses generating great internal shear forces in the suspension.Due to the shear forces the mineral particles rub against each other andare comminuted to such a particle size, that they may be used as afiller in paper manufacture.

FIGS. 2 and 3 disclose two process alternatives, which deviate from thephase subsequent to the dispersion stage of the mineral particles fromeach other. In both embodiments the material to be treated is obtainedas coarse reject of the last step of the vortex cleaning plant 32. Therejected coarse fraction is led via a pump 44 to a cleaner 46,preferably a so called Eliminator-cleaner, i.e. to the firstfractionation stage of the reject, in which the separated fine materialis returned to the feed of the pump 30 to be fractionated again in thevortex cleaning plant 32 and the coarse fraction is led at a highconsistency typical of the reject of the Eliminator-cleaner 46 to amixing/dispersion apparatus 48, in which the rotor(s), propellers orlike mix it generating differences in kinetic speed between theparticles, i.e. shear forces, due to which the material is dispersed.

In the embodiment of FIG. 2 subsequent to the dispersion stage takingplace in a mixing/dispersion apparatus 48 the mixture is diluted, pumpedwith a pump 50 to the cleaner 52, preferably a so calledEliminator-cleaner, to the last fractionation stage of the treatmentprocess and the dispersed mineral fractions are fractionated with avortex cleaner 52, from which the usable fractions are accepted so thatthey may be returned to the feed of the pump 30 to be reused in thevortex cleaning plant 32 and the coarse fraction is rejected either tobe retreated or to be totally rejected.

In the arrangement of FIG. 3 the separation of the usable and coarsefraction subsequent to the dispersion and dilution is carried out by ascreen-type apparatus 54, illustrated as a so called Micra-screen, inwhich the openings of the screen surface are chosen in such a way thatthe passed fraction is of its grain size such that it may be returned tothe feed of the pump 30 and the coarse fraction on the screen surface isdischarged from the process or led to further treatment.

The recycling and dispersion process of the dispersed mineral fractionsmay, of course, also be carried out in two or more stages. The coarsefraction, which is not dispersed in the first dispersion stage, may, ofcourse, be treated again and thus the mineral loss exiting from theprocess may be diminished, see FIGS. 4-7.

FIG. 4 illustrates an alternative for the embodiments of FIGS. 2 and 3,more accurately to their later stages. In other words, the reject from acleaner 46′ is discharged at a high consistency to a mixing/dispersingapparatus 48′, in which after the dispersion stage the material isdiluted and fed by a pump 44′ to the next cleaner 46″. The reject fromthe cleaner 46″ is led to the second mixing/dispersing apparatus 48″ andafter the dispersing stage and dilution by a pump 50 to a third cleaner46′″, from which the accept is fed as well as from the cleaner 46″ to bereused or to one of the previous cleaning/fractionating stages (feed ofthe cleaner 46′ shown as an example).

FIG. 5 illustrates the connection of two cleaners 56 and 56′ so that thereject of the latter cleaner 56′ may not only be completely dischargedfrom the system, but also part of it may be led back to amixing/dispersing tank 58 to be dispersed again, whereby the materiallosses may be in principle totally avoided.

FIG. 6 illustrates an embodiment, in which subsequent to a cleaner 66several subsequent mixing/dispersing apparatuses 68, 68′ and 68″ areprovided. Only after the described three-stage dispersion the materialis led by the pump 50 to a cleaner 66′, the accept of which is led to bereused or returned to the feed of the preceding cleaner 66 prior to thepump 44. The reject again is discharged either completely or it isfurther separately treated somewhere. However, it is completely possiblethat also the reject of the cleaner 66′ is returned to one of thepreceding refining stages for further refining. Moreover, it is possiblethat only two refining stages are provided, or more than three,completely depending on the need.

Also the refining treatment itself may be carried out either asone-stage or multistage process and at least in theory such a processmight be possible, in which coarse fraction is recirculated for such along time that also the possible sand, and like impurities are refinedand returned to the process, whereby the system might be completelyclosed.

FIG. 7 illustrates yet another embodiment, in which the reject of thecleaner 76 is led to a mixing/dispersing apparatus 78, which comprisesseveral superposed mixing zones. The material dispersed in the apparatus78 by the pump 50 is brought to the last fractionating stage in acleaner 79. The object is to disperse material more efficiently than ina one-stage mixing tank.

FIG. 8 illustrates an alternative to the embodiments of FIGS. 2 and 3.In FIG. 8 the coarse reject of the last vortex cleaning step 32, the ashcontent of which may be even 60-80%, is led by a pump 80 and dilutedwith recirculation water preferably containing as little solids aspossible, for example, with clear filtrate S from 0-fiber recovery, tothe feed of a curved screen 82, a so called Micra-screen. A screenhaving a slot width of, for example, 100 μm is used as the screensurface of the curved screen 82. The inlet flow is divided by the curvedscreen 82 into thicker fraction and filtrate. All coarse fiber, shivesand impurity fractions are discharged with the thicker fraction. Thefiltrate receives the filler particles which have passed through said100 μm slots and most of the water. The filtrate of the curved screen82, preferably diluted with recirculation water S containing as littlesolids as possible, is led by a pump 84 to the feed of the vortexcleaners 86. The accept of the vortex cleaners 86, which has most of thewater and the fine filler fraction having the size of less than 10 μm,is returned, for example, to the feed of the last vortex cleaning stepto the pump 88 or the reject thickening (broken line B). The reject ofthe vortex cleaning step 86 comprises filler fraction having theparticle size of more than 10 μm at a high solids content of about40-50%. Said reject is led, for example, with free drop, to a dispersionapparatus 90, in which the solid particles in the reject are subject togreat shear forces. The filler particles are split and the flow exitingthe dispersion apparatus 90 is mainly filler fraction having a usable,homogeneous size of less than 10 μm.

The filler fraction dispersed in the dispersion apparatus 90 is returnedby the pump 84 to the feed of the vortex cleaning stage 86 operating inthe above described manner. Thus the unrefined filler fraction may berecirculated in the dispersion apparatus 90 and vortex cleaners 86 untilthe filler particles are dispersed to a usable size.

FIG. 9 illustrates an alternative corresponding to the embodiment ofFIG. 8. The only significant difference to FIG. 8 is that a pressurescreen 92 is used instead of a curved screen, which in the same way asthe curved screen divides the reject coming from the vortex cleaningstep 32 to a coarse fraction to be discharged from the process and to afraction containing filler particles to be further treated, thetreatment of which is already illustrated in connection with FIG. 8. Itmust, however, be noted that by using pressure screen 92 it may bepossible to avoid the use of the pump 84 of FIG. 8, because the finefraction obtained from the pressure screen may be fed directly to thevortex cleaners 86. Another difference in FIG. 9 compared with FIG. 8 isthat the material refined in the dispersion apparatus 90 is returned tothe feed of the pressure screen 92 and not directly back to the vortexcleaners as in FIG. 8.

Of course, it is possible also in the embodiments of FIGS. 8 and 9 toconnect more screening stages and dispersion stages subsequently, forexample, as in FIG. 4. Further, it is also possible to lead thedispersed material from the dispersion apparatus 90, for example, to anew screening stage 94 (the whole part of the process is illustratedwith broken lines due to its alternative nature), from which the usablefine material is returned to use and the coarse fraction is rejected anddischarged from the system.

FIGS. 10a-10c illustrate the feed (FIG. 10a), the filtrate (FIG. 10b)and the reject (FIG. 10c) of the curved screen in the process. Itbecomes apparent in the drawings, how all the fibrous fraction and thelarge-sized filler particles from the feed in FIG. 10a have beenrejected to FIG. 10c and the filtrate, FIG. 10b, contains merely fillerfraction.

As may be seen from the above illustrated embodiments, which to someextent deviate from each other, new and previously unknown method andapparatus have been developed for treating recycled fibrous material sothat as much of the filler therein as possible might be recovered andreused. Firstly, it must be noted that all the apparatuses illustratedin the drawings and in the description are connected to each other withflow channels suitable for the particular purpose, by a mannerillustrated either in the drawings, or described in the description orclaims. Further, it must be noted that the above described embodimentsare only examples of many different variations of the invention and areby no means given to restrict the inventive concept, but are merelygiven as examples. Thus it is obvious that the mixing/dispersingapparatus in the above described embodiments is described as a tank,having at least one mixing/dispersing rotor, also grinders or mill-typecomminuters known per se may be used. It is also obvious that thedetails described in connection with different embodiments are availableto be used also in other embodiments without special notice. Thus theattached patent claims alone define the present invention.

I claim:
 1. A method of treating filler-containing material utilizing avortex cleaning plant having a plurality of steps including a last step,and utilizing a first fractionation stage and a last fractionation stagedistinct from the vortex cleaning plant, said method comprising thesteps of: (a) passing filler-containing material to the vortex cleaningplant including the last step thereof in which the material is dividedinto a first, finer, fraction and a second, coarser, fraction; (b)passing the second fraction to the first fractionation stage to dividethe second fraction into a third, fine, fraction, and a fourth, coarse,fraction; (c) returning the third fraction to the vortex cleaning plant;(d) dispersing the fourth fraction to produce dispersed material; (e)passing the dispersed material to the last fractionation stage; (f) inthe last fractionation stage, dividing the dispersed material into afifth, fine fraction and a sixth fraction; and (g) returning the fifthfraction to the vortex cleaning plant, or to be treated again in steps(b) or (e).
 2. A method as recited in claim 1 wherein steps (a) through(g) are practiced utilizing recycled fiber pulp as the filler-containingmaterial.
 3. A method as recited in claim 2 comprising the furthersteps, between steps (d) and (e), of: (h) dividing the recycled fibermaterial into a sixth fine fraction, and a seventh coarser fraction; (i)returning the sixth fraction to steps (a) or (b); and (j) dispersing theseventh fraction and using the dispersed seventh fraction in step (e).4. A method as recited in claim 3 wherein step (i) is practiced byreturning the sixth fraction to step (b).
 5. A method as recited inclaim 2 comprising the further step (h) of returning the sixth fractionto be dispersed in step (d).
 6. A method as recited in claim 2 whereinstep (d) is practiced by passing the fraction being dispersed intoseveral consecutive dispersion stages without any fractionation stagetherebetween.
 7. A method as recited in claim 2 comprising the furtherstep (h), between steps (d) and (e), of diluting the dispersed fraction.8. A method as recited in claim 2 wherein steps (a) and (b) arepracticed so that the fourth fraction has a consistency of greater than30% prior to the practice of step (d), and step (d) is practiced at aconsistency of greater than 30%.
 9. A method of treating recycled fiberpulp containing filler comprising the steps of: (a) passing the recycledpulp containing filler to a vortex cleaning plant having a plurality ofsteps including first and last steps; (b) in the last step of the vortexcleaning plant dividing the pulp into a first finer fraction, and asecond, coarser fraction; (c) returning the first fraction to the vortexcleaning plant; (d) screening the second fraction in a first screeningstage to separate the recycled fiber pulp into a third fractioncontaining shives and other wood-based material, and a fourth fractioncontaining filler material; (e) passing the fourth fraction to a secondscreening stage in which the fourth fraction is divided into a fifth,fine material, fraction and a sixth, coarse material, fraction; and (f)dispersing the sixth fraction in a dispersion stage.
 10. A method asrecited in claim 9 comprising the further step (g) of leading thedispersed sixth fraction from step (f) back to the second screeningstage in step (e).
 11. A method as recited in claim 9 comprising thefurther step (g) of leading the dispersed sixth fraction from step (f)back to the first screening stage in step (d).
 12. A method as recitedin claim 9 comprising the further step (g), after step (f), offractionating the dispersed fraction from step (f) into a seventh finefraction, and an eighth coarse fraction; (h) returning the seventhfraction to the vortex cleaning plant or to step (d); and (i) dispersingthe eighth fraction.
 13. A method as recited in claim 9 wherein steps(a) through (e) are practiced so as produce the sixth fraction at aconsistency of greater than 30%, step (f) being practiced at aconsistency of greater than 30%.
 14. Apparatus for treatingfiller-containing material comprising: a vortex cleaning plant includinga first treatment stage and a last treatment stage, said last treatmentstage comprising a fractionation stage producing a reject materialincluding filler-containing material; further treatment apparatusconnected to said vortex cleaning plant for treating the reject materialtherefrom, said treatment apparatus comprising at least one dispersingdevice for breaking the filler-containing material into smallerparticles; a pump and a first fractionation device between said at leastone dispersing device and said vortex cleaning plant; and a pump and asecond fractionation device on the opposite side of said at least onedispersing device from said first fractionation device; and means forreturning filler material broken into smaller particles to said vortexcleaning plant.
 15. Apparatus as recited in claim 14 wherein saidfurther treatment apparatus further comprises a first fractionationdevice connected between said vortex cleaning plant and said at leastone dispersing device.
 16. Apparatus as recited in claim 15 wherein saidfurther treatment apparatus comprises a second fractionating devicedisposed on the opposite side of said at least one mixing/dispersingdevice from said first fractionation device.
 17. Apparatus as recited inclaim 15 wherein said first fractionation device comprises a vortexseparator.
 18. Apparatus as recited in claim 14 wherein said at leastone dispersing device comprises a first mixing/dispersing device, andfurther comprising a second dispersing device connected on the oppositeside of said second fractionation device from said first dispersingdevice, and further comprising a pump and a third fractionation deviceconnected on the opposite side of the second dispersing device from saidsecond fractionation device.
 19. Apparatus as recited in claim 14wherein said second fractionation device contains a reject conduit, andwherein said reject conduit is connected to said dispersing device. 20.Apparatus as recited in claim 14 wherein said at least one dispersingdevice has at least two stages.
 21. Apparatus as recited in claim 14wherein said at least one dispersing device comprises a plate grinder,cone grinder, or mill grinder.
 22. Apparatus as recited in claim 14wherein said vortex cleaning plant is connected to the short circulationof a paper machine.
 23. Apparatus for treating filler-containingmaterial comprising: a vortex cleaning plant including a first treatmentstage and a last treatment stage, said last treatment stage comprising afractionation stage producing a reject material; and further treatmentapparatus connected to said vortex cleaning plant for treating thereject material therefrom, said treatment apparatus comprising at leastone mixing/dispersing device, said further treatment apparatuscomprising a first fractionation device connected between said vortexcleaning plant and said at least one mixing/dispersing device, and asecond fractionating device disposed on the opposite side of said atleast one mixing/dispersing device from said first fractionation device.24. Apparatus as recited in claim 23 wherein said second fractionationdevice comprises a vortex separator.
 25. Apparatus as recited in claim23 wherein said second fractionation device comprises a curved screen ora pressure screen, having a perforated or slotted screen plate. 26.Apparatus for treating filler-containing material comprising: a vortexcleaning plant including a first treatment stage and a last treatmentstage, said last treatment stage comprising a fractionation stageproducing a reject material including filler-containing material;further treatment apparatus connected to said vortex cleaning plant fortreating the reject material therefrom, said treatment apparatuscomprising first and second dispersing devices for breaking thefiller-containing material into smaller particles; a pump and a firstfractionation device connected between said vortex cleaning plant andsaid first and second dispersing devices; and a pump and a secondfractionation device connected on the opposite side of said first andsecond dispersing devices from said first fractionation apparatus; andmeans for returning filler material broken into smaller particles tosaid vortex cleaning plant.
 27. A method of treating filler-containingmaterial in a production process utilizing a vortex cleaning plant, thevortex cleaning plant having a plurality of steps including apredetermined step, and utilizing a first fractionation stage, amixing/dispersion stage, and a second fractionation stage operativelyassociated with the vortex cleaning plant, said method comprising thesteps of (a) passing filler-containing material to the vortex cleaningplant including the predetermined step thereof in which predeterminedstep the material is divided into a first, finer, fraction and a second,coarser filler rich fraction containing filler material; (b) passing thesecond filler rich fraction to the first fractionation stage to dividethe second fraction into a third, fine, fraction, and a fourth, coarsefiller rich fraction; (c) returning the third, fine, fraction to anearlier point in the production process; (d) dispersing the fourthcoarse filler rich fraction in the mixing/dispersion stage to producedispersed filler rich material; (e) passing the dispersed filler richmaterial from the mixing/dispersion stage to the second fractionationstage; (f) in the second fractionation stage, dividing the dispersedfiller rich material into a fifth, fine fraction and a sixth coarsefraction; and (g) returning the fifth fine fraction to an earlier pointin the production process.
 28. A method as recited in claim 27 wherein(g) is practiced by returning the fifth fraction to be treated again instep (b).
 29. A method as recited in claim 27 wherein steps (a) through(g) are practiced utilizing recycled fiber pulp as the filler-containingmaterial.
 30. A method as recited in claim 27 wherein steps (a) and (b)are practiced so that the fourth fraction has a consistency of greaterthan 30 % prior to the practice of step (d), and step (d) is practicedat a consistency of greater than 30 %.
 31. A method of treatingfiller-containing material in a production process utilizing a vortexcleaning plant, the vortex cleaning plant having a plurality of stepsincluding a predetermined step, and utilizing a mixing/dispersing stageand a fractionation stage which are operatively associated with thevortex cleaning plant, said method comprising the steps of: (a) passingfiller-containing material to the vortex cleaning plant including thepredetermined step thereof in which predetermined step the material isdivided into a first, finer, fraction and a second, coarser filler richfraction; (b) dispersing the second, coarser filler rich fraction in themixing/dispersing stage to produce dispersed filler rich material; (c)passing the dispersed filler rich material to the fractionation stage;(d) in the fractionation stage, dividing the dispersed filler richmaterial into a third, fine fraction and a fourth coarser fraction; and(e) returning the third fine fraction to an earlier point in theproduction process.
 32. A method as recited in claim 31 wherein step (e)is practiced to return the third fraction to the vortex cleaning plant.33. A method of treating filler-containing material utilizing a vortexcleaning plant, the vortex cleaning plant having a plurality of stepsincluding a step producing a coarse output, and utilizing amixing/dispersing stage and a fractionation stage operatively associatedwith the vortex cleaning plant, said method comprising the steps of: (a)passing filler-containing material to the vortex cleaning plantincluding the step producing a course filler rich output such that thecoarse filler rich output is divided into a first, finer, fraction and asecond, coarser filler rich fraction; (b) dispersing, in themixing/dispersing stage the second coarser filler rich fraction toproduce dispersed filler rich material; (c) passing the dispersed fillerrich material to the first fractionation stage; (d) in the firstfractionation stage, dividing the dispersed filler rich material into athird, fine fraction and a fourth coarser fraction; and (e) returningthe third, fine fraction to a point in the vortex cleaning plantupstream of the vortex step having the coarse output.
 34. Apparatus fortreating filler-containing material comprising: a vortex cleaning plantcontaining the filler-containing material, said vortex cleaning planthaving a plurality of stages and producing a reject filler-richmaterial, and further treatment apparatus operatively associated withsaid vortex cleaning plant for treating the reject material therefrom,said further treatment apparatus comprising: at least onemixing/dispersing device for dispersing the reject filler-rich material;a first fractionation device operatively associated with said vortexcleaning plant and upstream of said at least one mixing/dispersingdevice, wherein said first fractionation device is separate from saidmixing/dispersing device, and a second fractionating device disposed onan opposite side of said at least one mixing/dispersing device from saidfirst fractionation device.
 35. Apparatus as recited in claim 32 whereinsaid vortex cleaning plant is connected to a short circulation of apaper machine.
 36. Apparatus as recited in claim 32 wherein said atleast one dispersing device comprises a plate grinder, cone grinder, ormill grinder.